Transmission unit for a motor vehicle having two powered axles

ABSTRACT

A transmission system for a motor vehicle with two powered axles has an engine aligned perpendicular to the driving direction and a transmission parallel to the axis of the engine shaft and includes an angle gear housing flangemounted on the side of the transmission housing, both housings having a lubricant supply for centrifugal or splash lubrication of the corresponding gear parts. The lubricant supplies, which are separated from each other by a partition, are interconnected by at least one first partition opening which serves as a lubrication inlet and at least one second partition opening which serves as a lubrication return. The second partition opening is located not below a first horizontal plane which passes approximately through the lower edge of a shaft bearing arrangement in the partition for the connecting shaft and the first partition opening is located above a second horizontal plane which passes approximately through the uppermost second partition opening. In addition, a lubricant-collecting and -conducting device is located inside the transmission housing.

BACKGROUND OF THE INVENTION

This invention relates to transmissions for motor vehicles having twopowered axles and, more particularly, to transmissions for vehicleshaving an engine mounted transverse to the direction of travel andhaving a transmission with its centerline parallel to the engine shaft.

In such known transmissions, as described, for example, in GermanOffenlegungsschrift No. 33 17 247, one driven axle of the vehicle ispowered by an output drive gear which also serves as a flywheel for acentrifugal or injection lubricating system for the transmission. Topower the second driven axle of the vehicle, the drive system containsan angle drive connected to the transmission output drive gear by aconnecting shaft which may be a hollow shaft. The housing for the angledrive is arranged on the side of the transmission housing adjacent tothe output drive gear connection for the transmission and a shaftsupport for the connecting shaft leading from the output drive gear tothe angle drive preferably consists of tapered roller bearings mountedin a partition between the two housings. Both housings are filled with asupply of lubricant for centrifugal or injection lubrication of the gearparts contained therein.

The lubricant supply for a centrifugal and injection lubricatedtransmission should be so proportioned that adequate lubrication isprovided in each phase of operation while, at the same time, thequantity of lubricant used is limited to the minimum actually requiredso as to inhibit heating resulting from agitation that would impair thelubricating function of the lubricant. Problems can arise from this,particularly in the case of high-power angle drives, i.e., angle drivestransmitting a large amount of power.

In the first place, the interior volume of the angle drive is relativelysmall, compared to that of the transmission, and hence its lubricantcontent is correspondingly small. In the second place, a high-powertransmission always involves a correspondingly high evolution of heatwhich has to be removed by the lubricating oil. For reasons of space, aneffort is maintained to provide the greatest compactness, economy ofspace and small volume in the design of the angle gear but, at the sametime, the oil supply in the comparatively confined angle gear housingcannot easily be replenished. Any additional oil would escape throughthe bearings for the connecting shaft into the transmission housing,where the oil level when the vehicle is stationary is generally lowerthan the shaft bearings.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a motorvehicle transmission arrangement which overcomes the above-mentioneddisadvantages of the prior art.

Another object of the invention is to provide a transmission arrangementfor a vehicle with two driven axles which has a compact and space-savingconfiguration and requires minimum lubricant supply, even withhigh-power transmission, while providing adequate and dependablelubrication of the parts of the transmission and the angle gear in everyphase of operation of the vehicle.

These and other objects of the invention are attained by providinglubricant inlet and outlet openings in a partition separating thetransmission and angle drive compartments of the drive system to producea constant exchange of lubricant between the oil supplies in thetransmission and the angle drive during operation so that, despite acomparatively small supply in the angle drive, which would not by itselfbe sufficient for high-power operation with a conventional design,dependable and adequate lubrication of the angle drive is provided inall phases of operation.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the invention will be apparent from areading of the following description in conjunction with theaccompanying drawings in which:

FIG. 1 is a schematic illustration of the drive train of a motor vehiclehaving two powered axles and a transverse engine as well as atransmission system with its axis parallel to the engine shaft arrangedaccording to a representative embodiment of the invention;

FIG. 2 is a sectional view of the detail marked II in FIG. 1 at the lineof section marked II in FIG. 3;

FIG. 3 is a sectional view of the same detail looking in the directionof the arrow marked III in FIG. 2; and

FIG. 4 is an enlarged fragmentary view showing the detail marked IV inFIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the representative embodiment of a drive system of an all-wheel-drivemotor vehicle schematically illustrated in FIG. 1, one powered axle 6,which is the front axle, is driven continuously. The second powered axle7, which is the rear axle, is driven automatically by means of a Viskocoupling 28 disposed in a universal shaft 8 extending between the firstpowered axle 6 and the second powered axle 7 so that the two poweredaxles are substantially continuously coupled together torquewise.

An engine 1, mounted transversely to the direction of travel, has aclutch 5 and a transmission 3 with parallel axes at the output end ofthe engine. The wheels of the first powered axle 6 are driven directlyby way of a transmission output drive gear 9, a front-axle differential,not specially numbered, and conventional half driveshafts.

Driving the wheels of the second powered axle is accomplished by auniversal shaft 8 coupled to the transmission 3 by an angle drive 4. TheVisko coupling 28 transmits power from the shaft 8 to a rear axle gear,not specially numbered, and conventional rear wheel half driveshafts.

The transmission 3 and the angle drive 4 are structurally integrated ina transmission unit 2, the angle drive housing 11 being mountedlaterally on a transmission housing 12 at a location adjacent to theoutput drive gear 9. Each of the two gear housings 11 and 12 is filledwith a supply of lubricant for centrifugal or injection lubrication oftheir gear parts, the output drive gear 9 in the transmission 3 servingalso as a flywheel for such injection lubrication.

The angle drive 4 provided to transmit power to the second powered axle7 is driven by the output drive gear 9 through a connecting shaft 10. Inthe illustrated embodiment, the connecting shaft is a hollow shaft,mounted in the housing of the front axle differential, not speciallynumbered, which also supports the transmission output drive gear 9.

As illustrated in the sectional view of FIG. 2, the support for theconnecting shaft lo is a bearing consisting of two taper roller bearings21 and 22 mounted in two partition members 13 and 14 having a commonsurface 15 which separate a transmission compartment 16 and an anglegear compartment 17 from each other.

The partition members 13 and 14 thus separate the lubricant supplies forthe two gear compartments 16 and 17 from each other and a first wallopening 18 provides an oil inlet leading from the transmission 3 to theangle drive 4 while a second wall opening 19 provides an oil returnleading from the angle drive 4 to the transmission 3. Instead of onlyone such wall opening for each of the oil inlet and the return, severalsuch wall openings may be provided in each case, if required.

The second wall opening 19, providing the lubricant return, is locatedso that it does not extend below a first horizontal plane 20, shown inFIG. 3, which, passes approximately through the lower extremity 21a, 22aof the effective axial opening of the shaft bearings 21 and 22 in thepartition members 13 and 14 for the connecting shaft 10. On the otherhand, the first wall opening 18 which serves as an oil inlet, is locatedabove a second horizontal plane 23, passing adjacent to the top of thesecond wall opening 19. In FIG. 3, which shows an inside view of thepartition 13 on the angle drive side of the transmission housing 12,these spatial relations are clearly apparent.

Inside the transmission housing 12, as best seen in FIGS. 2 and 3, alubricant trap and conduit arrangement 24, consisting of guide ribs orthe like, is also provided to collect oil projected from the front-enddrive 9 for centrifugal or injection lubrication and divert it to thefirst wall opening 18. Because the first wall opening 18 is above thelevel of the lubricant in the angle drive housing, some of the lubricantoriginally contained in the transmission housing is conducted duringoperation into the comparatively confined angle drive housing 11. At thesame time, a portion of the lubricant supply in the angle drive housing11 is returned to the transmission housing 12 by way of the lower secondwall opening 19. This occurs when the oil level in the angle gearhousing rises above the first horizontal plane marked 20 in FIG. 3.

Through this constant circulation of oil between the lubricant suppliesin the two gear housings, a dependable and effective lubrication of theangle drive is provided, despite high-power operation of the angledrive. Even with highpower operation, no excessive heating of the angledrive lubricant supply will occur because, with a comparatively low oillevel in the angle drive, there will be no appreciable agitation to heatthe oil.

Instead of only one oil trap and oil conduit arrangement 24, a secondsimilar arrangement may, of course, be provided, if required.

Advantageously, the oil trap and conduit arrangement 24 can be anintegral component of a cast transmission housing 12. In principle, ofcourse, the oil trap and conduit arrangement may alternatively be aseparate component mounted in a suitable location inside thetransmission housing.

In the illustrated embodiment, the angle drive housing 11 is a separatecomponent mounted by lateral flanges to the transmission housing 12.This design is especially advantageous when the transmission unit has anordinary mass-production transmission housing for a motor vehicle havingonly one powered axle. However, the invention is not limited to suchdesigns.

In the case of transmission units with transmission and angle drivehousings flanged together, a secure seal must be provided at the commonsurface 15. In conventional transmission units which do not have theaforementioned wall openings, a sealing ring 29, shown in FIG. 2, isarranged in the radially interior region, close to the connecting shaft.It is evident that, in the arrangement of the two gear compartments 16and 17 with communicating wall openings 18 and 19, additional sealingmeasures are required. In principle, it would be conceivable for thispurpose to provide a corresponding sealing ring or the like in the outermarginal region of the parting joint. However, such a sealingarrangement would be comparatively expensive and complicated tomanufacture, because such a transmission unit will generally have anoncircular outer contour in the region of the common surface.

Advantageously, therefore, in the illustrated embodiment, each of thewall openings 18 and 19 is sealed from the outside, as shown in FIG. 4,in the region of the common surface 15 between the adjacent partitionmembers 13 and 14 of the two gear housings by a sealing ring 25, whichis preferably an O-ring.

To simplify assembly of the uncomplicated and comparatively smallsealing rings 25 still further, the wall openings of the one gearhousing, for example, those of the angle drive housing 11, may each havean encircling bevel 26 at their ends facing the other gear housing. Thebevels 26 provide partial accommodation of the sealing rings 25, whilethe partition of the adjacent gear housing, for example, thetransmission housing 12, has a planar surface in the region of the wallopenings.

Instead of an encircling bevel 26, the wall openings 18 and 19 mayalternatively be provided with a corresponding annular groove, ifdesired.

It will be advantageous if sleeves 27 projecting from this gear housingare mounted, for example, press-fitted, in the wall openings encircledby a bevel 26 or by a matching annular groove to serve as guides for thesealing rings 25. Such a sleeve is also illustrated in the sectionalview of FIG. 4.

Although the invention has been described herein with reference tospecific embodiments, many modifications and variations therein willreadily occur to those skilled in the art. Accordingly, all suchvariations and modifications are included within the intended scope ofthe invention.

We claim:
 1. A transmission system for a motor vehicle having twopowered axles comprising an engine disposed transversely to thedirection of vehicle travel, a first housing for a transmission with itsaxis parallel to the engine shaft, a transmission output drive gearmember acting a flywheel for driving a first powered axle, an angledrive connected to the transmission output drive gear member by aconnecting shaft and arranged in a second housing which is separatedfrom the first housing by a partition, a driveshaft leading from theangle drive to a second powered axle, bearing means for the connectingshaft provided in the partition, the second housing being mounted on thefirst housing adjacent to the transmission output drive gear, a supplyof lubricant in each of the first and second housings for lubrication ofthe parts therein, the lubricant supplies in the two housings beingseparated from each other by the partition, at least one first openingin the partition providing a lubricant inlet leading from the firsthousing to the second housing, and at least one second opening in thepartition providing a lubricant return leading from the second housingto the first housing, the second opening being located not below a firsthorizontal plane passing approximately through the bottom of theeffective axial opening for the connecting shaft, the first openingbeing located above a second horizontal plane passing approximatelythrough the top of the second opening, and at least one lubricant trapand conduit means in the first housing leading to the first opening andcooperating with the transmission output drive gear member which acts asa flywheel for the centrifugal lubrication so that lubricant projectedby the transmission output drive gear member is diverted toward thefirst opening.
 2. A transmission system according to claim 1 wherein thelubricant trap and conduit means is cast as an integral component of thefirst housing.
 3. A transmission system according to claim 1 wherein thesecond housing is a separate component flanged laterally to the firsthousing and the partition comprises two separate adjacent partitionmembers and including a sealing ring in the region of the commonsurfaces of the partition members of the two housings for sealing eachof the first and second openings from the outside.
 4. A transmissionsystem according to claim 3 wherein the first and second openings in thepartition member of one housing are each provided on the side toward theother housing with an encircling recess for partial accommodation of thecorresponding sealing ring while the adjacent partition member of theother housing has a plane surface in the region of the first and secondopenings.
 5. A transmission system according to claim 4 including asleeve protruding from each of the first and second openings providedwith a recess to serve as a guide.